The objective of this work is to synthesize and evaluate derivatives of biologically active compounds which localize in the myocardial muscle. The biologically active compound will be derivatized so that it contains a radionuclide carrying group; if the radionuclide carrying group is a chelating agent, the chelating portion of the resulting derivative will be designed to retain high affinity for a metallic radionuclide such as Tc99m. If the radionuclide is iodine it will be bound to an aromatic ring added to the structure of the biologically active compound. The overall aim will be a thorough and fundamental investigation of a small number of well chosen derivatives. As in the previous proposal the major emphasis will be placed on derivatives of beta adrenoceptor blocking agents. The development of such a derivative will allow, by external detection, production of an image of the spatial distribution of the adrenergic derivative within the intact heart. Such an early detection system for myocardial ischemia or necrosis might lead to a better prevention and treatment of the aspect of the general "coronary heart disease". An equally important outgrowth of this work would be the ability to serially quantify areas of ischemia for the evaluation of therapeutic regimens proposed to decrease overall permanent myocardial damage following acute coronary occlusion and clinical myocardial infarction.